This pilot study will assess potential improvements in the techniques presently used to determine transepithelial nasal membrane potential difference (PD). This membrane voltage, and the response of this voltage to a series of solution, differentiates between individuals who have cyctic fibrosis (CF) and those who do not. It is hypothesized that the proposed improvements will increase the signal to noise ratio (warm versus room temperature solutions) and eliminate the need for a sub-dermal reference needle (dermal abrasion). The reproducibility of measurements as catheter size is varied will also be evaluated. Nasal PD measurements will be performed on a series of CF and non-CF individuals to evaluate the effects of these modifications. It is anticipated that information from this study will contribute to the development of a standardized protocol which can be tested in a future multi-center study to validate the reproducibility of PD measurements. Such standardization is a necessary step in the validation of nasal PD as a surrogate outcome measure for multi-center clinical trails.